Let-off mechanism for warp knitting machines



Oct. 11, 1955 a. E. CLENTIMACK LET-OFF MECHANISM FOR WARP KNITTING MACHINES 2 Sheets-Sheet 1 Filed June 20, 1951 Oct. 11, 1955 G. E. CLENTIMACK LET-OFF MECHANISM FOR WARP KNITTING MACHINES 2 Sheets-Sheet 2 Filed June 20, 1951 Unite States Patent Office 2,720,094 Patented Oct. 11, 1955 LET-OFF MECHANESM FOR WARP KNITTING MACHINES George E. Clentimack, Plainville, Mass, assignor, by mesne assignments, to Draper Corporation, Hopedale, Mass, a corporation of Maine Application June 20, 1951, Serial No. 232,629

6 Claims. (Cl. 66-86) The present invention relates to improvements in a let-off mechanism adapted for use in a warp knitting machine for controlling the supply of warp yarns from the warp beam to the knitting instrumentalities of the machine.

The invention is embodied in a warp knitting machine of the general type in which individual warp threads or yarns are fed to yarn guides which move with relation to the knitting needles tocause each of the yarns to be presented to at least two or more needles and to be interknitted with each other to form successive connected knitted rows of courses of knitting in accordance with a desired pattern. The warp threads are guided as warps or sheets of warp threads, from one or more warp beams around tensioning rollers and thence to one or a plurality of series of yarn guides forming part of the knitting mechanism. It will be understood that the size and quality of the loops in each succeeding course of the knitted fabric is to a considerable extent controlled by the tension imposed on the feeding yarns.

Warp knitting machines are adapted for the knitting of knitted fabric which may be 15 feet or more in width utilizing for this purpose a row of needles of equal length, together with their cooperating knitting instrumentalities. In such machines a warp beam or warp beams of considerable size and weight are utilized for supplying simultaneously many hundreds and even thousands of knitting yarns.

Since any change in the tension of the feeding yarns has an instant effect upon the knitting and tends to cause undesirable transverse marks or streaks in the knitted goods, it is of critical importance to provide a let-off device for the machine which will avoid either slackening or tightening of the threads with attendant tension changes either during machine operation or in starting and stopping of the machine.

It is an object of the present invention to provide an improved power operated let-off machanism for warp knitting machine which will operate with a greater degree of precision and accuracy to maintain the desired relationship between the demand and supply of warp thread and which will eliminate to a greater extent any tension variation, particularly in starting and stopping, to produce a uniform appearing fabric.

In carrying out the present invention, a mechanically operated and controlled let-01f device is provided which takes the form of a variable speed drive for the warp beam which is constructed and arranged to maintain at all times an exact correspondence between the demand for thread by the knitting devices and the peripheral rate of let-off of warp thread from the thread mass on the warp beam. The input shaft of the variable speed mechanism is preferably geared to the operation of the main cam shaft of the machine so that the variable speed mechanism is started and stopped with the cam shaft and is driven at a rate which bears a definite relation to the rate of yarn consumption by the knitting devices. The variable speed mechanism which may be of the friction disc type is controlled by means of a double ended pawl and ratchet mechanism acting through a worm and nut connection, and a pawl shield which is movable from an intermediate neutral position to render the pawl and ratchet mechanism operative to shift the variable speed mechanism in either direction. The shield is connected to be acted upon by the tension roller so that movement of the tension roller induced by a reduction in the amount of yarn between the warp beam and knitting devices causes the pawl to act upon the ratchet in one direction to increase the rate of letoif, and a movement of the tension roller induced by an excessive supply of yarn causes the ratchet to be operated in the opposite direction to decrease the rate of let-off. The rate at which the correction takes place will correspond with the extent of movement of the tension roller from its intermediate position, since a greater movement of the roller will be accompanied by correspondingly increased movement of the shield which will uncover a correspondingly greater surface of the ratchet to be acted upon by the reciprocating pawl. Further in order to maintain the efiiciency in the operation of the correcting mechanism as the diameter of the thread mass decreases and the rate of rotation of the warp beam is correspondingly increased through the operation of the variable speed mechanism, the rate of reciprocation of the pawl is proportioned to the rate of rotation of the beam. To this end the pawl is connected to be driven directly in timed relation to the rotation of the beam.

In the drawings illustrating the invention,

Fig. l is a somewhat fragmentary end view taken on the line 1-1 of Fig. 2 illustrating particularly the let-off housing with the casing thereof sectioned to show underlying parts and only enough of a portion of the warp knitting machine shown to illustrate the connection of the present invention therewith;

Fig. 2 is a sectional view taken on a line 2-2 of Fig. 1 showing the mechanical variable speed drive and associated gearing and the outer end of the warp beam driven thereby; and

Fig. 3 is an enlarged detail view illustrating in solid lines the shield, and pawl actuated thereby, and the operating connections including an accentric on the warp beam shaft as shown in Fig. l for imparting continuous reciprocatory movements to the correcting pawl.

Referring to the drawings, the knitting instrumentalities of a conventional warp knitting machine are generally shown in Fig. l as including a unitary row of needles 10 mounted on a vertically movable needle bar 12, front and rear sets of yarn guides 14 and 16, web holders l8 and a movable presser bar 24). The yarn guides 14 are mounted on a guide bar 22 supported on arms 24 for rocking and for axial movement on a supporting shaft 26 which is in turn mounted for vertical movement bodily on arms 28. The rear yarn guides 16 are similarly mounted on a guide bar 3%) supported on arms 32 for axial and rotational movement on a shaft center 34 carried on the supporting arms 28. A warp beam is indicated at 36 in Fig. 1 from which warp yarns are supplied to the yarn guide series 14. The warp beam 36 is carried on a warp beam shaft 38 rotatably supported in bearings of which one bushed bearing 40 is shown at 40 in Fig. 2, on the machine frame 42. The warp yarns are drawn from the Warp beam 36 over an idler roller 44 around a tension roller 46 and thence downwardly to the guides 14. Further in accordance with the usual practice, the tension roller 46 is carried on arms 48 mounted on a rock shaft 50 supported on the machine. A tensioning strain is imparted upwardly to the arms 48 and roller 46 to tension the roller against the yarns by means of tensioning springs which may be of any ordinary description and are not specifically here shown.

The let-off mechanism provided in accordance with the invention comprises a gear assembly for driving the warp beam shaft 38 housed in a gear box 54. Power is suppliedto the gear assembly by means of an input shaft 56 (see Fig. 1) connected to be driven by the machine, being preferably driven from the main cam shaft 51 of the machine through a sprocket chain 52 and sprockets 53 and 55. The spiral gear 58 on the input shaft 56 meshes with a spiral gear 60 on a rearwardly extending shaft 62 which, together with a series of spaced discs 64 mounted thereon forms the driving element of a disc type variable speed mechanism. Other parts of the variable speed drivinge mechanism include a driven shaft 66 and a series of spaced discs 68 mounted thereon, and an interposed adjustable element in the form of a shaft 70 supporting a series of tapered discs 72 which mesh respectively with the driving discs 64 and driven discs 68. The displace able shaft 70 is carried on a bracket 76 formed on one arm of a bell crank adjusting lever 78 supported to turn on a fixed pivot 80. Compression springs 82 coiled about the shaft 70 between the tapered discs 72 and the flanges of the supporting bracket 76 cause the tapered discs to engage against the respective driving discs 64 and driven discs 68 with an engaging pressure which is determined by the strength of the respective springs.

The driven shaft 66 of the variable speed mechanism is coupled to a worm shaft 86 on which is mounted a worm 8S meshing with a worm gear 90 loose on the reduced end of the warp beam shaft 38. The shaft 38 is driven from the worm gear 90 through back gearing which includes a gear 92 keyed to the sleeve hub of worm gear 90, a driven gear 94 secured to the warp beam shaft 38, and two gears 96, 98 secured to a countershaft 100 and arranged to mesh respectively with gears 92 and 94.

The mechanism provided for correcting or adjusting the variable speed drive for adjusting the supply to the demand for warp thread by the knitting devices comprises a nut 104 threaded to an adjusting screw 106 formed on a rotatable adjusting shaft 108. The nut 104 is pivotally connected to the forked end of the upwardly extending arm of the bell crank adjusting lever 78. The rotation of the adjusting shaft in one direction to depress the inteiposed adjustable portion of the variable speed bearing consisting of the tapered plates 72 has the effect of increasing the rate of drive of the driven warp beam. Rotation of the adjusting shaft 108 in the opposite direction so that the nut travels to the right serves to raise the interposed tapered discs 72 of the variable speed mechanism and causes the warp beam to be driven at a proportionately lower speed. Rotation of the adjusting shaft 108 is effected by means of a ratchet 110 keyed to the adjusting shaft 108 and a double ended pawl 112 pivotally supported on one arm of a pawl actuating lever 114 which is supported to loosely turn on the adjusting shaft 108. Continuous reciprocatory movement is imparted to the pawl lever 114 and pawl 112 through a fixed are by means of an eccentric disc 116 on the reduced hub of warp beam supporting shaft 38, and a link 118 connected at one end to a second arm of the pawl lever 114 and at its other end provided with a strap engaging the periphery of the eccentric disc 116. In this construction it will be noted that the pawl 112 is continuously reciprocated through a fixed are when the warp beam is rotating and at a speed which bears a direct relation to the rate of rotation of the warp beam.

The operation of the ratchet and pawl mechanism above described is controlled from the tension roller 46 by means of a pawl shield 120 interposed between the ratchet 110 and double pawl 112. The shield is mounted on an upwardly extending arm 122 formed on a sleeve hub 124 which is loose on shaft 108 and is externally supported in a bearing formed in the machine frame 42. A second upwardly extending arm 126 formed on the sleeve hub 124 externally of the casing 54 is connected by means of a link 128 with an upwardly extending arm 130 formed integrally with one of the take-up lever arms 48 for the take-up shaft 50 and tension roller 46 thereon. In order that the positioning device above described may not be affected by the relative small jiggling movements of the tension roller forward and back, a friction connection having a limited freedom of play is provided between the upwardly extending arm 130 and link 128. This connection comprises a friction element 136 pivoted to the arm 130 for sliding friction engagement with the link 128 and two stop collars 138, 140 on the link 128 to limit the extent of such movement.

The operation of the let-off device as above described is briefly as follows. Assuming that the machine is in operation and that the tension roller 46 occupies a perfectly adjusted neutral position, the shield 120 will occupy also the intermediate neutral position shown in Figs. 1 and 3 in which the double ended pawl 112 continuously oscillated from the warp beam shaft 38 rides on the surface of the shield for the full extent of the pawl movement in each direction. This condition will obtain when the rate of let-off from the warp beam is exactly adjusted to the demand for thread from the warp knitting mechanism. Assuming now that as the diameter of the thread mass on warp beam 36 decreases the rate of let-off becomes insufficient to supply the demand of the knitting devices for thread, the tension roller 46 will be depressed, causing the shield 120 to be moved to the right, thus uncovering a portion of the ratchet 110, which will be engaged by the left hand end of the double pawl 112. Stepped movement of the ratchet in a counterclockwise direction as shown in Fig. 1 now takes place. Nut 104 travels to the left on screw 106 from the position shown in Fig. 2, thus moving the disc assembly 72 comprising the adjusting element of the variable speed drive downwardly to increase the rate of drive of the warp beam 36. It will be understood that as the tension roller 46 moves by a lesser or greater amount from its neutral position, the corresponding movement imparted to the shield will cause a stepped advancing movement of correspondingly lesser or greater extent to be imparted to the ratchet 110 with each reciprocation with the pawl. The rate of correction is thus adjusted in accordance with the extent of corrective movement required to bring the tension roller 46 back to its neutral position. As the tension roller 46 returns to its neutral position, the shield 120 also returns to its intermediate position, thus rendering the pawl 112 inoperative.

In the event that the let-off of warp threads tends to overrun the demand, an upward movement of the tension roller 46 will result which will cause the double pawl 120 to be moved to the left, thus uncovering a portion of the ratchet 110 for engagement by the right hand side of the pawl 112. Under these conditions the nut 104 will be caused to travel to the right from the position shown in Fig. 2 to raise the disc assembly 72 of the variable speed mechanism, and thus to slow the rate of drive of the warp beam 36. As the thread mass on the warp beam 36 decreases in diameter, the warp beam will be driven through the mechanism described at a substantially faster rate in order to maintain a constant rate of let-off of the warp yarn. The pawl 112 and the pawl lever 114 will, at the same time, be driven at an increasingly rapid rate so that the rate at which correction takes place will be proportionately increased with the rate of rotation of the warp beam. In this manner the operation of the correcting mechanism is maintained at substantially the same efficiency irrespective of changes in the rate of drive imparted to the warp beam.

The preferred embodiment of the invention having been described, what is claimed is:

1. In a warp knitting machine having warp knitting devices, actuating means for the machine including a cam shaft, a warp beam from which warp threads are supplied to the knitting devices, and a movable tension roller engaging a portion of the warp extending between the beam and the knitting devices, a let-off device Which comprises a mechanical drive between the cam shaft and the warp beam providing a continuous drive of the warp beam from the cam shaft and including a variable speed driving mechanism having a speed adjusting element shiftable in opposite directions to produce alternatively a higher and a lower speed ratio between the cam shaft and the beam, and a correcting device for controlling the position of said adjusting element including a control element having an intermediate neutral position in which the correcting device is inoperative and shiftable in opposite directions to render the correcting device operative for moving the speed adjusting element in a corresponding direction. and means connected to the control element to be moved by the tension roller whereby movement of the control element by the roller from an intermediate adjusted neutral position in either direction will render the correcting device operative to move the speed adjusting element in the corresponding direction.

2. In a warp knitting machine having warp knitting devices, actuating means for the machine including a cam shaft, a warp beam from which warp threads are supplied to the knitting devices, and a movable tension roller engaging a portion of the warp extending between the beam and the knitting devices, a let-off device which comprises a mechanical drive between the cam shaft and the warp beam providing a continuous drive of the warp beam from the cam shaft and including a variable speed driving mechanism having a speed adjusting element shiftable in opposite directions to produce alternatively a higher and a lower speed ratio between the cam shaft and the beam, and a correcting device for controlling the position of said adjusting element including a ratchet, a worm and nut actuating connection between the ratchet and the adjusting element, a double pawl acting on the ratchet, means for imparting a reciprocatory movement to the double pawl, a movable shield for the pawl having a neutral position in which the pawl is inoperative, and a connection between the shield and tension roller whereby movement of the shield with the tension roller from said netural position in either direction will render the pawl effective to turn the ratchet in the corresponding direction.

3. In a warp knitting machine having warp knitting devices, actuating means for the machine including a cam shaft, a warp beam from which warp threads are supplied to the knitting devices, and a movable tension roller engaging a portion of the warp extending between the beam and the knitting devices, a let-off device which comprises a variable speed driving mechanism connected between the cam shaft and the warp beam including a speed adjusting element shiftable in alternate directions to produce alternatively a higher and a lower speed ratio between the cam shaft and the warp beam, and a correcting device for controlling the position of said adjusting element including an actuator driven in fixed timed relation to the warp beam and further shiftable between a neutral and alter nate operative positions, a control element for controlling the shifting of said actuator having an intermediate neutral position in which said actuator is inoperative and alternate operative positions in which the actuator is effective to move the speed adjusting element in opposite directions, and means connected to the control element to be moved by the tension roller whereby movement of the control element by the roller from an intermediate adjusted neutral position in either direction will render the actuator operative to move the speed adjusting element in the corresponding direction.

4. In a warp knitting machine having warp knitting devices, a warp beam from which warp threads are supplied to the knitting devices, and a movable tension roller engaging a portion of the warp extending between the beam and knitting devices, a let-off device which comprises a variable speed driving mechanism including a driving element driven in timed relation with the knitting devices, and a speed adjusting element: connecting said driving element with the warp beam shiftable to adjust the driving ratio between the driving element and the warp beam, and a correcting device for controlling the position of said adjusting element including a ratchet operatively connected with the adjusting element, a double pawl connected to be reciprocated in timed relation from the warp beam, a movable shield for the pawl having a neutral position in which the double pawl is inoperative, and means connecting the shield to be moved by the tension roller whereby movement of the shield by the tension roller from an intermediate adjusted neutral position in either direction will render the pawl effective to turn the ratchet in the corresponding direction.

5. In a warp knitting machine having warp knitting devices, a warp beam from which warp threads are supplied to the knitting devices, and a movable tension roller engaging a portion of the warp extending between the beam and knitting devices, a let-oif device which comprises a variable speed driving mechanism including a multiple disc driving element continuously driven in timed relation with the knitting devices, a multiple disc driven element, a multiple tapered disc adjusting element meshing with said driving and driven multiple disc elements and shiftable to adjust the driving ratio therebetween, an irreversible worm and gear driving connection between the driven element and the warp beam, and a correcting device for controlling the position of said adjusting element including a ratchet, a worm and nut actuating connection between the ratchet and the adjusting element, a double pawl acting on the ratchet, an eccentric driving connection driven in timed relation to the warp beam for reciproeating the pawl, a movable shield for the pawl having a neutral position in which the pawl is inoperative, and a. connection between the shield and tension roller whereby movement of the shield with the tension roller from said neutral position in either direction will render the pawl effective to turn the ratchet in the corresponding direction.

6. In a warp knitting machine having warp knitting devices, actuating means for the machine including a cam shaft, a warp beam from which warp threads are supplied to the knitting devices, and a movable tension rod engaging a portion of the warp extending between the beam and the knitting devices, a let-off device which comprises a mechanical drive between the cam shaft and the warp beam providing a continuous drive of the warp beam from the cam shaft and including a variable speed driving mechanism having a speed adjusting element shiftable in opposite directions to produce alternatively a higher and a lower speed ratio between the cam shaft and the beam, and a correcting device for controlling the position of said adjusting element including a control element having an intermediate neutral position in which the correcting device is inoperative and shiftable in opposite directions to render the correcting device operative for moving the speed adjusting element in a corresponding direction, and means connected to the control element to be moved by the tension rod whereby movement of the control element by the rod from an intermediate adjusted neutral position in either direction will render the correcting device operative to move the speed adjusting element in the corresponding direction.

References Cited in the file of this patent UNITED STATES PATENTS 2,100,680 Wirth Nov. 30, 1937 2,340,889 Klumpp et al. Feb. 8, 1944 2,448,035 Lambach Aug. 31, 1948 2,541,192 Blake Feb. 13, 1951 FOREIGN PATENTS 625,894 Great Britain July 6, 1949 

